The objective of this project is to study the properties of allospecific T specific T cell lines. Recent cloning experiments have shown that clones of one of the lines are of Lyt 1 plus, Lyt 2 minus phenotype and are able to perform at least three different functions. They lyse spleen blast cell targets, cooperate with B cells for a humoral response to SRBC, and if injected with stimulator cells into the footpad of mice, will evoke a dealyed type hypersensitivity reaction. These results, while they show that the Lyt phenotype is not related to the function of T cells and that T cells may be polyfunctional, raise the question how a killer cell can cooperate with B cells for a humoral response. This is probably possible via factors which are released from T cells. In current experiments we are studying the properties of these factors. Factors are not only released from T cells upon specific allogeneic stimulation but also by transformed derivatives of these T cell lines. This makes possible large scale preparation of this activity. The goals of our experiments are three-fold: First, we want to purify the factor by gel filtration, DEAE chromatography, isoelectric focussing and polyacrylamide electrophoresis. Second, we want to study the effects of the purified factor on B cells. Third, we want to try to use this factor in the establishment of permanent B cell lines.